The distribution of male and female tissues was recorded for 22 adult cuticular structures in 1574 gynandromorphs from 16 gynandromorph-producing queen honeybees (Apis mellifera). The frequency of mosaicism was calculated, and 0-46.67% mosaicism was found for the 22 structures. A mathematical model, developed previously for determining Drosophila primordial cell number (Nissani & Lipow, 1977), was used to calculate from the frequency of mosaicism and total number of blastoderm cells the number of primordial blastoderm cells forming each structure. For an estimated 3700 blastoderm cells, the number of primordial cells ranged from 1 to 214 for the structures examined. The appropriateness of this model to the honeybee is discussed and estimates of cell numbers for equivalent structures in Drosophila and the honeybee are compared.